Pattern forming material of a siloxane polymer

ABSTRACT

A pattern forming material contains a siloxane polymer having the general formula: ##STR1## [wherein R, R&#39; and R&#34; are the same or different and are respectively one member selected from hydrogen, an alkyl group or a phenyl group; X is one member selected from fluorine, chlorine, bromine, iodine and a --CH 2  Y group (wherein Y is one member selected from chlorine, fluorine, bromine, iodine, an acryloyloxy group, a methacryloyloxy group, and a cinnamoyloxy group); and l, m and n are respectively 0 or a positive integer, l and m not being simultaneously 0]. The material has a high sensitivity to high-energy radiation, a high contrast, and an excellent resistance to reactive ion etching under oxygen gas. The material is conveniently used as a negative resist for forming a submicron pattern having a high aspect ratio.

This is a division of application Ser. No. 580,468 filed Feb. 15, 1984,now U.S. Pat. No. 4,507,384.

BACKGROUND OF THE INVENTION

The present invention relates to a pattern forming material and, moreparticularly, to a silicone based negative resist, and to a method forforming a submicron pattern having a high aspect ratio using such aresist.

In the manufacture of ICs and LSIs, organic compositions containing apolymeric compound and called a resist are frequently used. Morespecifically, a substrate to be processed is covered with a selectedorganic composition as a resist film. The resist film is irradiated witha high-energy beam in a predetermined pattern to form an electrostaticlatent image in the resist film. Development is then performed to form apatterne resist film. Thereafter, the substrate is immersed in anetching solution to chemically etch the exposed portion of the substratewhich is uncovered by the resist pattern, or to dope an impuritytherein.

However, with a recent tendency toward higher integration of ICcircuits, further minimization is desired. In wet etching methods usingan etching solution, the problem of side etching is inevitable. In viewof this problem, dry etching such as reactive ion etching using a gasplasma is becoming popular. However, conventional resist materials arethemselves etched during dry etching of the substrate; thus the resistfilm must be thick to allow selective etching of the substrate. For thisreason, a resist material with a high dry etching resistance has beendesired. However, a resist material which is satisfactorily resistant todry etching has not yet been proposed.

Meanwhile, in order to provide a multilayered wiring layer or asemiconductor element of a three-dimensional array structure, it isdesired to form a resist pattern on a nonplanar substrate. The resistfilm must be made thick to level a step.

Furthermore, in order to trap highly accelerated ions before they reachthe substrate, the resist film must again be thick. However, with aconventional resist material, resolution is lowered as the filmthickness increases, preventing formation of a fine pattern.

In order to solve this problem, a method has been proposed wherein aresist is applied in a multilayered structure to form a resist patternhaving a high aspect ratio. According to such a method, a thick film ofan organic polymeric material is formed as a first layer. A thin resistmaterial film is formed thereover as a second layer. The second, resistlayer is selectively irradiated with a high-energy beam and isdeveloped. The resultant pattern is used as a mask to dry etch theorganic polymeric material of the first layer and to form a pattern of ahigh aspect ratio. With this method, when a conventional resist materialis used for the second layer, the ratio of dry etch rates of thematerials of the first and second layers, that is, the selectivity,cannot be set to be high. Akiya et al (article to be published in 43rdProceedings of the Japan Association of Applied Physics, p. 213)reported that when a multilayer pattern consisting of a first layer ofpolymethyl methacrylate (to be referred to as PMMA hereinafter) and asecond layer of chloromethylated polystyrene is dry etched using carbontetrachloride as an etching gas, the selectivity can be selected to bevery high and a resist pattern having a high aspect ratio can be formed.However, in this case, the etch rate of the PMMA is also low; it takes along time to etch a thick PMMA film. Carbon tetrachloride as an etchantalso etches the underlying substrate.

A three-layered structure has also been proposed as a multilayeredresist pattern obtained using an oxygen plasma, and consists of a first,thick layer of an organic polymeric material, a second layer of aresist, and a third layer which consists of an inorganic material havinga high resistance to the oxygen plasma and formed between the first andsecond layers. In this case, the pattern of the resist material is usedas a mask to dry etch the inorganic material using a gas such as carbontetrachloride, carbon tetrafluoride or argon. Subsequently, using theresultant inorganic material pattern as a mask, the organic polymericmaterial layer is dry etched using oxygen. With this method, the oxygenplasma can quickly etch the first, thick organic polymeric materiallayer and the substrate is not etched at all. Accordingly, a resistpattern of a desired profile may be formed without requiring monitoringof the end timing of etching. However, this method requires a largenumber of steps.

When a silicone based resist having a high resistance to dry etchingusing an oxygen plasma is used for the second layer, an oxygen plasmacan be used to dry etch the organic polymeric material of the firstlayer, using the resist pattern of the second layer as a mask. For thisreason, a resist pattern of a high aspect ratio can be formed within ashort period of time and with a small number of steps. However, acurrently available silicone based resist has a glass transitiontemperature considerably lower than room temperature. A conventionalsilicone based resist having a low molecular weight is in liquid ormilky form, is difficult to handle, and has a low sensitivity tohigh-energy radiation.

On the other hand, a conventional silicone based resist having a highmolecular weight is in a rubbery form, is easier to handle, and has ahigher sensitivity to high-energy radiation. However, the resultantpattern frequently has an undulation due to swelling in a developingsolvent, resulting in a low resolution. Furthermore, a functional grouphaving a high chain reaction property such as a vinyl group isintroduced to improve sensitivity of the cross-linking reaction. Thisalso results in a low resolution.

SUMMARY OF THE INVENTION

The present invention has been made in consideration of this and has forits object to provide a high-energy radiation-sensitive, negative resistwhich has a high sensitivity, a high resolution, and a high dry etchingresistance, and a method for forming a pattern with such a negativeresist.

According to an aspect of the present invention, there is provided apattern forming material containing a siloxane polymer having thegeneral formula: ##STR2## [wherein R, R' and R" are the same ordifferent and are respectively one member selected from the groupconsisting of hydrogen, an alkyl group and a phenyl group; X is onemember selected from the group consisting of fluorine, chlorine,bromine, iodine and a --CH₂ Y group (wherein Y is one member selectedfrom the group consisting of chlorine, fluorine, bromine, iodine, anacryloyloxy group, a methacryloyloxy group, and a cinnamoyloxy group);and l, m and n are respectively 0 or a positive integer, l and m notbeing simultaneously 0].

According to an another aspect of the present invention, there is alsoprovided a method for forming a pattern, comprising the steps of forminga high-energy radiation-sensitive material film on a substrate;selectively irradiating a surface of the high-energy radiation-sensitivematerial film with a high-energy beam; and removing by developing anon-irradiated portion of the high-energy radiation-sensitive materialfilm with a developing solvent, wherein the high-energyradiation-sensitive material is a siloxane polymer having theabove-mentioned general formula.

According to still another aspect of the present invention, there isalso provided a method for forming a pattern, comprising the steps offorming an organic polymeric material layer on a substrate; forming ahigh-energy radiation-sensitive material film thereover; selectivelyirradiating a surface of the high-energy radiation-sensitive materialfilm so as to cross-link a high-energy radiation-sensitive material atan irradiated portion of the high-energy radiation-sensitive materialfilm; removing a non-irradiated portion of the high-energyradiation-sensitive material film using an organic developing solvent;and etching a portion of the organic polymeric material layer notcovered with the remaining, irradiated portion of the high-energyradiation-sensitive material film by dry etching using oxygen and theremaining, irradiated portion as a mask, thereby forming a pattern ofthe organic polymeric material layer, wherein the high-energyradiation-sensitive material contains a siloxane having theabove-mentioned general formula.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing the relationship between molecular weight andsensitivity;

FIG. 2 is a graph showing an infrared absorption spectrum of a siloxanepolymer prepared in Working Example 1 of the present invention; and

FIG. 3 is a graph showing the relationship between the electron beamdose and the normalized remaining film proportion, which represents theelectron beam sensitivity of a resist pattern formed by a method of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The alkyl group in the general formula of the polysiloxane of thepresent invention can be a methyl group, an ethyl group, a propyl groupor the like. In order to increase a glass transition temperature Tg, thecontent of the phenyl group in the general formula is preferably 75% ormore of the side chain residues.

The content of the phenyl group in which a functional group (X in theabove-mentioned general formula) is introduced, is preferably 20% ormore of the side chain residues. Sensitivity increases with an increasein the weight average molecular weight. FIG. 1 is a graph showing therelationship between the molecular weight and a minimum exposure as anindex of sensitivity. In FIG. 1, the weight average molecular weight Mwis plotted along the axis of abscissa, and sensitivity (C/cm²) isplotted along the axis of ordinate. As can be seen from FIG. 1, sincethe sensitivity preferably decreases within a range of 10⁻⁴ to 10⁻⁷C/cm², the molecular weight preferably increases within a range of 2×10³to 2×10⁶.

The most important feature of the present invention is that ahigh-energy radiation-sensitive material having a high sensitivity andhigh resolution is obtained by introducing a functional group X into asilicone polymer having a phenyl group, such as polyphenylmethylsiloxaneor polydiphenylsiloxane. The phenyl group-containing silicone polymerexhibits a high resistance not only to oxygen gas but also to an etchantgas used in reactive ion etching such as CCl₄ or CF₂ Cl₂. A siliconebased polymer of which the content of the phenyl group is 75% or more issolid at room temperature and is soluble in an organic solvent such astoluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, ormonochlorobenzene. When a solution of such a silicone based polymer isapplied to a substrate by spin coating, an excellent film can be formed.This excellent solubility of a silicone based polymer containing aphenyl group allows selection from a wide variety of coating solvents ordeveloping solvents in accordance with the material of the substrate.This excellent solubility of a silicone based polymer containing aphenyl group is not impaired upon introduction of a functional group X.Accordingly, in contrast to a conventional silicone based resist whichis in a rubbery form, the silicone based resist of the present inventionis easy to handle. The constituent components, features and effects ofthe silicone polymer of the present invention may be summarized as inTable 1 below.

                                      TABLE 1                                     __________________________________________________________________________    Constituent                                                                   component                                                                            Feature       Effect                                                   __________________________________________________________________________     ##STR3##                                                                            Highly resistant to oxygen dry etching                                                      Only a thin film pattern need be formed for dry                               etching an underlying polymer. High resolution is                             obtained due to such small thickness of the film                              pattern.                                                  ##STR4##                                                                            High glass transition temperature (Tg)                                                      General silicone has a Tg lower than room                                     temperature and has a rubbery or liquid form. The                             material of the present invention has a Tg higher                             than 150° C. and is in a form equivalent to a                          conventional resist. Handling is easy and high                                resolution is obtained.                                  Functional                                                                           Forms network structure at                                                                  High sensitivity                                         group  low exposure                                                           __________________________________________________________________________

Regarding a method for preparing a polymer having the above-mentionedgeneral formula, a method may be adopted wherein a cyclic phenylsiloxanesuch as hexaphenylcyclotrisiloxane or octaphenylcyclotetrasiloxane issubjected to ring-opening polymerization by a hydroxide of an alkalimetal such as potassium hydroxide or an alkylate of an alkali metal suchas butyl lithium, and a functional group X is introduced into theresultant polydiphenylsiloxane. A cyclic phenylsiloxane may be usedsingly or may be copolymerized withtetramethyltetraphenylcyclotetrasiloxane oroctamethylcyclotetrasiloxane. When it is desired to form a pattern ofhigh resolution, a monodisperse polymer must be prepared wherein themolecular weight of the dispersed particles is uniform. Such amonodisperse polymer may be prepared by subjecting a cyclohexane toanionic living polymerization by a catalyst such as butyl lithium andintroducing a functional group X into the resultant polymer.

The siloxane polymer having the above-mentioned general formula may beprepared by reacting a phenyl group-containing siloxane oligomer or aphenyl group-containing polysiloxane having a small molecular weightwith a group X in the above-mentioned general formula or a compoundcontaining X under the presence of a Friedel-Crafts catalyst.

A siloxane polymer containing a chloromethyl group may be prepared byreacting a phenyl group-containing siloxane oligomer or a phenylgroup-containing polysiloxane having a small molecular weight with achloromethyl lower alkyl ether under the presence of a Friedel-craftscatalyst.

The raw material to be used in the preparation of the siloxane polymeras described above can be a polyphenyl group-containing siloxane havinga small molecular weight, which is prepared by polymerizing with an acidor an alkali a phenyl group-containing cyclic silicone oligomer such ashexaphenylcyclotrisiloxane or octaphenylcyclotetrasiloxane.Alternatively, there may be employed a phenyl group-containing siloxaneoligomer such as polydiphenylsiloxane or polydimethyldiphenylsiloxane. AFriedel-Crafts catalyst to be used herein can be a generalFriedel-Crafts catalyst such as aluminum chloride, ferric chloride,boron trifluoride, zinc chloride, stannic chloride, or titaniumtetrachloride. The chloromethyl lower alkyl ether can be chloromethylmethyl ether, chloromethyl ethyl ether or the like.

The siloxane polymer having the above-mentioned general formula isprepared by dissolving a phenyl group-containing siloxane oligomer or aphenyl group-containing polysiloxane having a small molecular weight ina chloromethyl lower alkyl ether, adding a Friedel-Crafts catalyst tothe resultant solution, and reacting the solution at a reactiontemperature falling within the range from -10° C. to room temperature.The reaction can be performed in a solvent such as carbon tetrachlorideor trichloroethane.

The reaction is terminated after 30 minutes to 30 hours, precipitationin methanol is performed, and reprecipitation is repeated in aketone-alcohol system. A molecular weight of the phenyl group-containingpolysiloxane can be controlled in accordance with the raw materialconcentration, catalyst temperature, reaction temperature, and reactiontime.

Polymerization may be attributed to the following four factors. (1) Aschloromethylation progresses, the chloromethyl group is molecularcross-linked with a nonsubstituted phenyl group. (2) Molecularcross-linking is caused by the reaction between the OH group at theterminal end and the chloromethyl group. (3) Dehydration condensationbetween the OH groups at the terminal ends is caused by the presence ofthe Friedel-Crafts catalyst. (4) Cross-linking between the OH group atthe terminal end and the phenyl group is caused by the presence of theFriedel-Crafts catalyst.

The siloxane polymer of the present invention has a high glasstransition temperature and can form a uniform film. Furthermore, thesiloxane polymer of the present invention contains a chloromethyl grouphaving a high sensitivity to high-energy radiation such as an electronbeam, has a phenyl group resistant to a gas plasma such as carbontetrachloride or carbon tetrafluoride, and has a siloxane structurehighly resistant to an oxygen gas plasma. Accordingly, the siloxanepolymer of the present invention can be used as a high-energyradiation-sensitive resist material.

The developing solvent to be used in a method for forming a patternaccording to the present invention can be a ketone such as methyl ethylketone, diisobutyl ketone, or methylisobutyl ketone; an aromatichydrocarbon such as benzene, toluene, xylene, or monochlorobenzene; anester such as ethyl acetate, n-amyl acetate, isoamyl acetate, methylcellosolve acetate, or ethyl cellosolve acetate; a cellosolve such asmethyl cellosolve or ethyl cellosolve; a mixture thereof with analcohol, e.g., methanol, ethanol or isopropyl alcohol, or with analiphatic hydrocarbon such as cyclohexane, n-hexane or n-heptane.

Working Examples for preparation of a high-energy radiation-sensitivematerial and a raw material thereof, and a method for forming a patternusing the thus prepared material will now be described.

WORKING EXAMPLE 1

A glass tube was charged with 50 g of octaphenylcyclotetrasiloxane, 100ml of tetrahydrofuran and 250 mg of potassium hydroxide. After the tubewas degassed and sealed, the reaction was performed at a polymerizationtemperature of 70° C. for 24 hours. The contents of the tube were pouredinto a water/methanol (1:4) solution to provide a white polymer. Thepolymer was purified by repeated reprecipitation in a methanol-xylenesystem. The resultant polydiphenylsiloxane was found to have a weightaverage molecular weight Mw of 1.3×10³, a molecular weight distributionMw/Mn of 2.6 and a glass transition temperature of 150° C.

Twenty grams of the polydiphenylsiloxane were dissolved in 500 ml of achloromethyl ether, and the reaction was performed using 20 ml ofstannic chloride as a catalyst at a temperature of -5° C. for 10 hours.The reaction solution was poured into the methanol to provide a whitepolymer. FIG. 2 shows the infrared absorption spectra of the polymer.Referring to FIG. 2, the number of waves (cm⁻¹) or the wavelength (μm)is plotted along the axis of abscissa, and the transmittance is plottedalong the axis of ordinate. As may be seen from FIG. 2, absorption dueto the presence of the disubstituted phenyl is observed at 800 cm⁻¹, andabsorption due to the presence of the methylene group of thechloromethyl group is observed at 2,200 cm⁻¹, thus confirming thechloromethylation. Elemental analysis of the polymer revealed that thepolymer had a degree of chloromethylation of 20%. From gel permeationchromatography, it was found that the polymer had a weight averagemolecular weight Mw of 1.2×10⁴ and a molecular weight distribution Mw/Mnof 1.8, providing a molecular weight increase of about 10-fold.

WORKING EXAMPLE 2

Twenty-five grams of the polydiphenylsiloxane obtained in WorkingExample 1 were dissolved in 500 ml of a chloromethyl methyl ether. Thesolution was reacted at -5° C. for 12 hours using 25 ml of stannicchloride as a catalyst. The reaction solution was poured into methanolto provide a white, solid polymer. Elemental analysis of the polymerrevealed that the polymer had a degree of chloromethylation of 17%. Thepolymer had a weight average molecular weight Mw of 4.7×10⁴ and amolecular weight distribution Mw/Mn of 3.5, providing a molecular weightincrease of about 40-fold.

WORKING EXAMPLE 3

A polymer was prepared using a mixture oftetraphenyltetramethylcyclotetrasiloxane andoctaphenylcyclotetrasiloxane in place of theoctaphenylcyclotetrasiloxane in Working Example 1, while varying themixing ratios. Chloromethylation was performed under the conditions ofWorking Example 2. Table 2 shows the phenyl group content, glasstransition temperature and molecular weight.

                  TABLE 2                                                         ______________________________________                                              Phenyl    Glass      Degree of                                                group     transition chloro-   Molecular                                Sample                                                                              content   temperature                                                                              methyla-  weight                                   No.   (%)       (°C.)                                                                             lation    (× 10.sup.4)                       ______________________________________                                        1     100       160        45        1.2                                      2     85        100        43        3.4                                      3     75         30        33        2.0                                      4     50        -20        21        1.1                                      ______________________________________                                    

WORKING EXAMPLE 4

Ten grams of hexaphenylcyclotrisiloxane were added to 3.7 ml of highlyconcentrated sulfuric acid and 10 ml of diethyl ether, and the resultantmixture was stirred at room temperature for 24 hours. Twenty millilitersof diethyl ether and 10 ml of water were added to the mixture, and theresultant mixture was stirred again for 1 hour. After removing the lowerlayer of water and drying the upper layer product with anhydridepotassium carbonate, the product was heated under reflux at 300° C. for3 hours. The ether was evaporated to provide a white solid material. Thesolid material was purified by reprecipitation with a methyl ethylketone-methanol solution to provide a polydiphenylsiloxane having aweight average molecular weight Mw of 1.9×10⁴ and a molecular weightdistribution Mw/Mn of 2.1.

WORKING EXAMPLE 5

Ten grams of hexaphenylcyclotrisiloxane were dissolved in 100 ml oftoluene. After sufficient degassing and dehydration, 5 ml of a 10%solution of butyl lithium in toluene were added dropwise to performliving polymerization at -60° C. for 10 hours. The reaction solution waspoured into methanol to provide a white, solid polymer. The polymer wasrepeatedly reprecipitated in a methyl ethyl ketone-methanol solution tobe purified, and was then vacuum dried. The weight average molecularweight Mw and the molecular weight distribution Mw/Mn of the polymerdetermined by gel permeation chromatography were 8.9×10³ and 1.1,respectively.

WORKING EXAMPLES 6 & 7

The polydiphenylcyclosiloxane (Working Example 6) obtained in WorkingExample 4 and the polydiphenylsiloxane (Working Example 7) obtained inWorking Example 5 were chloromethylated under the same reactionconditions and procedures as in Working Example 1. In Working Example 6,the resultant polymer had a degree of chloromethylation of 17%, a weightaverage molecular weight Mw of 3.1×10⁴, and a molecular weightdistribution Mw/Mn of 2.5. In Working Example 7, the resultant polymerhad a weight average molecular weight Mw of 2.2×10⁴ and a molecularweight distribution Mw/Mn of 1.3.

WORKING EXAMPLE 8

Chloromethylated polydiphenylsiloxanes having different degrees ofchloromethylation were obtained by changing the amount of stannicchloride to be added in Working Example 1. Table 3 below shows theamount of stannic chloride added, the degree of chloromethylation, theweight average molecular weight, and the molecular weight distribution.

                  TABLE 3                                                         ______________________________________                                               Amount    Degree of                                                           stannic   chloro-   Weight average                                     Sample chloride  methyla-  molecular Dispersi-                                No.    added     tion      weight    bility                                   ______________________________________                                        5      10        30        1.1 × 10.sup.4                                                                    1.7                                      6      20        45        1.2 × 10.sup.4                                                                    1.8                                      7      30        50        1.3 × 10.sup.4                                                                    1.9                                      8      40        55        1.5 × 10.sup.4                                                                    2.1                                      ______________________________________                                    

WORKING EXAMPLE 9

Polydiphenylsiloxanes having different molecular weights were preparedby varying the reaction temperature in Working Example 1. Subsequently,chloromethylated polydiphenylsiloxanes having different molecularweights and having the same degree of chloromethylation were obtainedfollowing the same procedures as those in Working Example 1. Table 4below shows the molecular weights and degrees of chloromethylation ofthe polydiphenylsiloxanes, and the molecular weights and molecularweight distribution of the chloromethylated polydiphenylsiloxanes.

                  TABLE 4                                                         ______________________________________                                                                       Molecular                                                                     weight of                                                   Molecular         chloro-                                                     weight of Degree of                                                                             methylated                                                                            Molecular                                    Tem-   polydi-   chloro- polydi- weight                                 Sample                                                                              pera-  phenyl-   methyla-                                                                              phenyl- distri-                                No.   ture   siloxane  tion    siloxane                                                                              bution                                 ______________________________________                                         9     40    0.7 × 10.sup.3                                                                    41      0.9 × 10.sup.4                                                                  1.6                                    10     70    1.3 × 10.sup.3                                                                    46      1.2 × 10.sup.4                                                                  1.8                                    11    100    5.8 × 10.sup.3                                                                    45      3.3 × 10.sup.4                                                                  1.9                                    12    140    9.6 × 10.sup.3                                                                    47      6.2 × 10.sup.4                                                                  2.1                                    ______________________________________                                    

EXAMPLE 1

The chloromethylated polydiphenylsiloxane obtained in Working Example 1was dissolved in methyl isobutyl ketone. The resultant solution wascoated on a silicon wafer with a thickness of about 0.5 μm, and thewafer was prebaked in a nitrogen flow at 100° C. for 20 minutes. Afterprebaking, the wafer was subjected to irradiation with an electron beamat an acceleration voltage of 20 kV. The wafer was then developed in asolvent mixture of methyl ethyl ketone:isobutyl alcohol (4:1), and wasrinsed with isopropyl alcohol. FIG. 3 shows the relationship between theproportion of film remaining and the electron radiation dose. Morespecifically, FIG. 3 shows the electron radiation sensitivitycharacteristics of the resist pattern wherein the electron radiationdose (C/cm²) is plotted along the axis of abscissa and the normalizedproportion of remaining film is plotted along the axis of ordinate. Asmay be seen from this graph, the electron radiation dose at which 50% ofthe initial film thickness remains is 2.0×10⁻⁵ C/cm², providing apractically satisfactory sensitivity. The γ-value, which is an index ofresolution and which is a slope of the sensitivity curve, is as high as2.5 as shown in FIG. 3. When the pattern after irradiation with anelectron beam was rinsed with the developing solution of the samecomposition, no residue or bridge was formed in a 0.5 μm line-spacepattern. Thus, a satisfactory resolution was obtained.

EXAMPLE 2

AZ-1350 resist (Shipley Co., Inc.) was applied on a silicon wafer to athickness of 2 μm. The resist coating was heated at 200° C. for 30minutes to be insoluble. The chloromethylated polydiphenylsiloxaneobtained in Working Example 1 was coated to a thickness of about 0.3 μmas in Example 1, and the coating was prebaked in a nitrogen flow at 100°C. for 20 minutes. After prebaking, the polymer was irradiated with anelectron beam at an acceleration voltage of 20 kV. The polymer wasdeveloped in a solvent mixture of methyl ethyl ketone:isopropyl alcohol(4:1) and was rinsed in isopropyl alcohol. As a result, a siloxanepolymer pattern of 0.3 μm line/space was formed on the AZ resist.Etching was performed using oxygen gas as an etchant gas and using aparallel plate-type sputtering etching apparatus (50 W applicationpower, and 80 millitorr oxygen gas internal pressure in the etchingchamber). Under these etching conditions, the etch rate of thechloromethylated polydiphenylsiloxane was 0, and the etch rate of the AZresist was 800 Å/min. The AZ resist pattern portion which was notcovered with the chloromethylated polydiphenylsiloxane was completelyetched away after etching for 28 minutes. After the etching process, apattern of 0.3 μm line/space pattern was left to have a thickness of 2.3μm.

EXAMPLES 3 TO 5

In the method of Example 1, irradiation was performed with an X-ray(Example 3), deep ultraviolet (Example 4), and an ion beam (Example 5),in place of the electron beam. Table 5 below shows the high-energyradiation doses at which 50% of the initial film thickness remained.

                  TABLE 5                                                         ______________________________________                                                                High-energy radiation                                 Example Radiation source                                                                              does                                                  ______________________________________                                        1       Electron beam: 10 kV                                                                          2.0 × 10.sup.-5 C/cm.sup.2                              acceleration voltage                                                  3       X ray/CuL ray: 13.3 Å                                                                     120 mJ/cm.sup.2                                       4       Deep ultraviolet                                                                               62 mJ/cm.sup.2                                               1 kW Xe-Hg lamp                                                       5       Ion beam Ga: 34 kV                                                                            1.0 × 10.sup.-6 C/cm.sup.2                      ______________________________________                                    

EXAMPLES 6-9

The chloromethylated polydiphenylsiloxane obtained in Working Example 8was irradiated with an electron beam following the procedures ofExample 1. Table 6 below shows the electron beam dose (sensitivity) atwhich 50% of the initial film thickness remained, and the γ-value.

                  TABLE 6                                                         ______________________________________                                               Degree of                                                                     chloro-                                                                       methyla-   Molecular  Sensitivity                                      Example                                                                              tion       weight     (C/cm.sup.2)                                                                           γ-value                           ______________________________________                                        6      30         1.1 × 10.sup.4                                                                     2.0 × 10.sup.-5                                                                  2.5                                     7      45         1.2 × 10.sup.4                                                                     2.0 × 10.sup.-5                                                                  2.5                                     8      50         1.3 × 10.sup.4                                                                     1.9 × 10.sup.-5                                                                  2.2                                     9      55         1.5 × 10.sup.4                                                                     1.8 × 10.sup.-5                                                                  2.1                                     ______________________________________                                    

EXAMPLE 10

The chloromethylated polydiphenylsiloxane obtained in Working Example 9was irradiated with an electron beam following the procedures ofExample 1. Table 7 below shows the electron beam dose (sensitivity) atwhich 50% of the initial thickness remained, and the γ-value.

                  TABLE 7                                                         ______________________________________                                        Molecular                                                                     weight       Sensitivity (C/cm.sup.2)                                                                    γ-value                                      ______________________________________                                        0.9 × 10.sup.4                                                                       3.0 × 10.sup.-5                                                                       2.7                                                1.2 × 10.sup.4                                                                       2.0 × 10.sup.-5                                                                       2.5                                                3.3 × 10.sup.4                                                                       7.2 × 10.sup.-6                                                                       2.1                                                6.2 × 10.sup.4                                                                       3.1 × 10.sup.-6                                                                       1.9                                                ______________________________________                                    

EXAMPLES 11-14

The pattern formed by the method in Example 1 was etched by RIE usingCF₄ (Example 11), CCl₄ (Example 12), CCl₂ F₂ (Example 13), and Ar(Example 14). Table 8 below shows the etch rates for the respectiveExamples.

                  TABLE 8                                                         ______________________________________                                        Example Etching gas                                                                             Etching conditions                                                                            Etch rate                                   ______________________________________                                        11      CF.sub.4  30 millitorr pressure ×                                                                 10 Å/min                                                  0.5 W/cm.sup.2 power                                        12      CCl.sub.4 20 millitorr pressure ×                                                                 0 Å/min                                                   0.5 W/cm.sup.2 power                                        13      CCl.sub.2 F.sub.2                                                                       40 millitorr pressure ×                                                                 0 Å/min                                                   0.7 W/cm.sup.2 power                                        14      Ar        30 millitorr pressure ×                                                                 0 Å/min                                                   0.3 W/cm.sup.2 power                                        ______________________________________                                    

WORKING EXAMPLE 10

Ten grams of a hexaphenylcyclotrisiloxane were dissolved in 100 ml oftoluene. After sufficient degassing and sealing, 5 ml of a 10% solutionof butyl lithium in toluene was dropwise added, and livingpolymerization was performed at -60° C. for 24 hours. The reactionsolution was poured into methanol to provide a white, soliddiphenylsiloxane polymer. The polymer was repeatedly precipitated in amethyl ethyl ketone-methanol solution to be purified, and was vacuumdried. The polymer has a weight average molecular weight Mw of 1.9×10⁴and a molecular weight distribution Mw/Mn of 1.1.

WORKING EXAMPLE 11

Twenty grams of the polydiphenylsiloxane prepared in Working Example 10were dissolved in 500 ml of chloromethyl methyl ether. The solution wasreacted at a temperature of -5° C. for 10 hours using 20 ml of stannicchloride as a catalyst. The reaction solution was then poured intomethanol to provide a white, solid chloromethylated diphenylsiloxanepolymer. Infrared absorption spectra of the polymer revealed absorptionat 800 cm⁻¹ due to the presence of disubstituted phenyl and absorptionat 2,200 cm⁻¹ due to the presence of the methylene group of thechloromethylene group, thus confirming chloromethylation. Elementalanalysis of the polymer revealed that the polymer had a degree ofchloromethylation of 45%. The polymer had a weight average molecularweight Mw of 4.2×10⁴ and a molecular weight distribution Mw/Mn of 1.3.

WORKING EXAMPLE 12

Six grams of the diphenylsiloxane polymer prepared in Working Example 10were dissolved in 20 ml of chloroform. After adding 0.04 g of ferricchloride and 0.01 g of iodine to the solution mixture, 9.9 g of chlorinegas was blown into the solution mixture for 24 hours. After thereaction, a white, chlorinated diphenylsiloxane polymer was obtained.The polymer had a chlorine content of 36%, a weight average molecularweight Mw of 2.2×10⁴ and a molecular weight distribution Mw/Mn of 1.2.

WORKING EXAMPLE 13

Ten grams of the diphenylsiloxane polymer prepared in Working Example 10were dissolved in 50 ml of chloroform. After adding 2 g of ferricchloride, 16 g of bromine were added dropwise for 4 hours to thesolution mixture. After leaving the solution mixture to stand for oneday, the solution mixture was poured into methanol, and a pale brownbrominated diphenylsiloxane polymer was obtained. The polymer had adegree of bromination of 35%, a weight average molecular weight Mw of3.2×10⁴, and a molecular weight distribution Mw/Mn of 1.2.

WORKING EXAMPLE 14

Five-point-two grams of the diphenylsiloxane prepared in Working Example10 were dissolved in 150 ml of nitrobenzene. After adding 5.1 g ofiodine, 1.9 g of iodic acid, 5 ml of carbon tetrachloride, 5 ml ofhighly concentrated sulfuric acid, and 5 ml of water, the resultantmixture was stirred at 90° C. for 35 hours. After the reaction, themixture was poured into methanol containing a small amount of dilutedsulfuric acid. A pale yellow iodinated diphenylsiloxane polymer in acotton like form was obtained. The polymer had a degree of iodination of50%, a weight average molecular weight Mw of 4.5×10⁴, and a molecularweight distribution Mw/Mn of 1.2.

WORKING EXAMPLE 15

Thirty grams of the chloromethylated diphenylsiloxane polymer preparedin Working Example 11 were dissolved together with 36 g of potassiumbromide in 150 ml of N,N-dimethylformamide. After stirring the mixtureat 80° C. for 4 hours, a large amount of a water-methanol mixture waspoured into the mixture, leaving a bromomethylated diphenylsiloxanepolymer as a precipitate. Substantially 100% of chloromethyl groups ofthe polymer had been converted into bromomethyl groups. The polymer hada weight average molecular weight Mw of 5.0×10⁴ and a molecular weightdistribution Mw/Mn of 1.3.

WORKING EXAMPLE 16

Thirty grams of the chloromethylated diphenylsiloxane polymer preparedin Working Example 11 were dissolved together with 55 g of potassiumiodide into 150 ml of N,N-dimethylformamide. An iodomethylateddiphenylsiloxane polymer was prepared following the procedures ofWorking Example 15. The polymer had a weight average molecular weight Mwof 6.2×10⁴ and a molecular weight distribution Mw/Mn of 1.3.

WORKING EXAMPLE 17

Thirty grams of the chloromethylated diphenylsiloxane polymer preparedin Working Example 11 were dissolved in 150 ml of pyridine. 0.25 mole ofacrylic acid was added dropwise to the mixture at 10° C. over 3 hours,and the resultant mixture was left to stand for 3 hours. After thereaction, the mixture was poured into methanol to provide an acryloyloxymethylated diphenylcyclosiloxane polymer as a precipitate. The polymerhad a weight average molecular weight Mw of 4.8×10⁴ and a molecularweight distribution Mw/Mn of 1.3.

WORKING EXAMPLE 18

0.25 mole of methacrylic acid was added dropwise in the same manner asin Working Example 17 to obtain a methacryloyloxy methylateddiphenylsiloxane polymer. The polymer had a weight average molecularweight Mw of 5.2×10⁴ and a molecular weight distribution Mw/Mn of 1.3.

WORKING EXAMPLE 19

0.25 mole of calcium cinnamate was added dropwise in the same manner asin Working Example 17 to obtain a cinnamoyloxy methylateddiphenylsiloxane polymer. The polymer had a weight average molecularweight Mw of 5.9×10⁴ and a molecular weight distribution Mw/Mn of 1.3.

EXAMPLE 15

A high-energy radiation-sensitive material prepared in Working Examples12 to 29 was dissolved in methyl isobutyl ketone, and the resultantsolution was applied on a silicon wafer to a thickness of about 0.5 μm.The coated film was prebaked in a nitrogen flow at 100° C. for 20minutes. The wafer was then irradiated with an electron beam at anacceleration voltage of 20 kV. The radiation pattern was a pattern forobtaining a sensitivity curve. The wafer was then developed in a solventmixture of methyl ethyl ketone:isopropyl alcohol (4:1), and was rinsedin isopropyl alcohol. Table 9 shows the electron beam dose at which 50%of the initial film thickness remained as an index of sensitivity, andthe γ-value as an index of resolution.

                  TABLE 9                                                         ______________________________________                                        Sample    12      13    14    15  16   17  18    19                           ______________________________________                                        Sensitivity D.sub.50                                                                    6       20    12    16  10   2   3     5                            (μC/cm.sup.3)                                                              γ-value                                                                           2.6     2.5   2.3   2.8 2.4  1.2 1.5   2.0                          ______________________________________                                    

A pattern for evaluating the resolution was irradiated with an electronbeam and was developed. Table 13 below shows a mimimum line/space whichallowed resolution without forming a residue or bridge.

                  TABLE 10                                                        ______________________________________                                        Sample      12    13      14  15  16   17  18    19                           ______________________________________                                        Minimum pattern                                                                           0.5   0.5     0.5 0.4 0.5  1.0 1.0   0.8                          size (μm)                                                                  ______________________________________                                    

EXAMPLE 16

AZ-1350 resist (Shipley Co., Inc.) was applied to a thickness of 2 μm ona silicon wafer and the wafer was heated at a temperature of 200° C. for30 minutes. A high-energy radiation-sensitive material used in Example15 was coated thereon in the same manner as in Example 15 to a thicknessof about 0.3 m. The wafer was prebaked at 100° C. in a nitrogen flow for20 minutes. After prebaking, the wafer was irradiated with an electronbeam at an acceleration voltage of 20 kV. The wafer was developed in asolvent mixture of methyl ethyl ketone:isobutyl alcohol (4:1), and wasrinsed in isopropyl alcohol. A 0.3 μm line/space pattern was thus formedon the AZ resist. Etching was performed in an oxygen gas using aparallel plate-type sputtering apparatus (excluding the materials ofWorking Examples 17, 18 and 19) at an application power of 50 W, anetching chamber pressure of 80 millitorr, and an oxygen gas flow rateof50 msec. Under these etching conditions, the etch rate of theradiation-sensitive siloxane polymer was substantially zero. The etchrate of the AZ resist was 800 Å/min, and the AZ resist was completelyetched away in 28 minutes. After the etching process, a 0.3 μmline/space pattern was formed to have a thickness of 2.3 μm.

For the materials of Working Examples 17, 18 and 19, a 0.7 μm line/spacepattern was formed on the AZ resist. The AZ resist was etched in oxygengas by the method as described above. A 0.7 μm line/space pattern wasformed to have a thickness of 2.3 μm after etching.

EXAMPLES 17-19

In the method of Example 15, an X-ray (Example 17), a far ultravioletray (Example 18), and an ion beam (Example 19) were used in place of anelectron beam. Table 11 shows the energy beam dose at which 50% of theinitial film thickness remained.

                  TABLE 11                                                        ______________________________________                                        Radiation         Sample                                                      Example source        12     13   14   15   16                                ______________________________________                                        17      X-ray/CuL ray:                                                                              100    250  180  210  150                                       13.3 Å (mJ/cm.sup.2)                                              18      Deep ultraviolet: 1                                                                          52    140   92  105   75                                       kW Xe-Hg lamp                                                                 (mJ/cm.sup.2)                                                         22      Ion beam Ga: 34 kV                                                                          1.0    3.0  2.0  2.5  1.5                                       (μC/cm.sup.2)                                                      ______________________________________                                    

The high-energy radiation-sensitive materials used were those used inExamples 12, 13, 14, 15 and 16.

EXAMPLE 20

Irradiation with an ultra high-voltage mercury lamp was performed inplace of irradiation with an electron beam in the method of Example 15.Table 12 shows the minimum dose at which 100% of the initial thicknesswas exposed.

                  TABLE 12                                                        ______________________________________                                        Sample            17        18    19                                          ______________________________________                                        Minimum Dose (mJ/cm.sup.2)                                                                      10        25    50                                          ______________________________________                                    

A high-energy radiation-sensitive material obtained in Working Examples12 to 16 had a low sensitivitity and did not form a pattern at a dose of3 J/cm² or more.

In the above Examples, chlorine, bromine and iodine are used as halogenelements. However, it is to be understood that a similar effect may beobtained with fluorine.

A silicone based resin, that is, a siloxane polymer, obtained inaccordance with the present invention has a higher glass transitiontemperature than that of a conventional silicone based resin, and has ahigh sensitivity to and a high resolution under high-energy radiation.Since a cyclic siloxane monomer can be subjected to livingpolymerization, a resist material which has a small molecular weightdistribution, that is, a high resolution, can be obtained. The resin ofthe present invention is in a white powdery form, has a good solubility,and a good coating property by spin coating. The resin of the presentinvention is thus easy to handle as compared with a conventionalsubstantially liquid silicone based resin.

If the resin of the present invention is used as an upper layer of abilayered resist having a thick organic lower layer, a submicron patternhaving a very high aspect ratio can be formed.

The above advantages of the resin of the present invention contributemuch to the manufacturing techniques of semiconductor elements and thelike.

In a conventional negative resist, a bridge or the like is easily formeddue to proximity effect, swelling during development and the like. Whensuch a resist is micronized, desired fine patterning cannot be achieved.However, the resin of the present invention is not liable to suchproximity effect and swelling, and thus has a high resolution. Thiseffect is particularly notable when the resist has a bilayeredstructure. Manufacture of a bilayered structure requires a smallernumber of manufacturing steps and a shorter manufacturing time ascompared to manufacture of a multilayered structure having three or morelayers. In a conventional multilayered structure, a thick film patterncannot be formed with a high resolution since the upper layer resist hasa low resolution and a low dry etching resistance. However, when theresist of the present invention is used, a pattern of a high resolutionand a high aspect ratio can be formed. Accordingly, a pattern which hasa sufficient thickness to allow pattern covering of a step or to allowhigh-speed ion-implantation, and which has at the same time a highresolution, can be formed in a short period of time and at low cost witha resist of the present invention.

What is claimed is:
 1. A pattern forming material containing a siloxanepolymer having the general formula: ##STR5## [wherein R, R' and R" arethe same or different and are respectively one member selected from thegroup consisting of hydrogen, an alkyl group and a phenyl group; X isone member selected from the group consisting of fluorine, chlorine,bromine, iodine and a --CH₂ Y group (wherein Y is one member selectedfrom the group consisting of chlorine, fluorine, bromine, iodine, anacryloyloxy group, a methacryloyloxy group, and a cinnamoyloxy group);and l, m and n are respectively 0 or a positive integer, l and m notbeing simultaneously 0].
 2. A material according to claim 1, wherein aphenyl group content is not less than 75% of side chain residues.
 3. Amaterial according to claim 1, wherein X is --CH₂ Cl in the generalformula.
 4. A material according to claim 1, wherein the siloxanepolymer is prepared by reacting one member selected from the groupconsisting of a phenyl group-containing siloxane oligomer and a phenylgroup-containing polysiloxane having a low molecular weight with onemember selected from the group consisting of X in the general formulaand a compound containing X in the general formula under the presence ofa Friedel-Crafts catalyst.
 5. A material according to claim 3, whereinthe siloxane polymer is prepared by reacting one member selected fromthe group consisting of a phenyl group-containing siloxane oligomer anda phenyl group-containing polysiloxane having a low molecular weightwith a chloromethyl lower alkyl ether under the presence of aFriedel-crafts catalyst.
 6. A material according to claim 5, wherein thechloromethyl lower alkyl ether is one member selected from the groupconsisting of chloromethyl methyl ether and chloromethyl ethyl ether.